Hydrogenation of halonitroaromatic compounds

Abstract

Process for preparing haloaromatic amines by catalytic hydrogenation of the corresponding halonitroaromatic compounds, characterized in that iron-containing Raney nickel is used as catalyst, where the haloaromatic amines prepared can be used for the synthesis of photographic couplers which are useful in photographic emulsions or elements.

We claim: 
     
       1. A process for preparing a haloaromatic amine by catalytic hydrogenation of the corresponding halonitroaromatic compound, wherein iron-containing Raney nickel is used as catalyst and wherein the halonitroaromatic compound corresponds to the formula (I) and the corresponding haloaromatic amine corresponds to the formula (II) ##STR13## where A is an aromatic radical to which the NO 2  group in formula (I) or the NH 2  group in formula (II) is bonded via a ring carbon atom of an aromatic ring and where at least one ring carbon atom of an aromatic ring of the radical A is substituted by at least one halogen atom and wherein the ring A is further substituted with a substituent selected from the group consisting of hydroxy, alkyl, alkoxy, aryloxy, aryl, formyl, alkonoyl, cycloalkanoyl, aroyl, alkanoyloxy, cycloalkanoyloxy, aroyloxy, alkylsulphonyl, cycloalkylsulphonyl, arylsulphonyl, alkylnoylamino, cycloalkylamino, aroylamino, alkylsuphonamido, cycloalkylsulphonamido, arylsuphonamido, alkoxycarbonyl, cycloalkoxycarbonyl, aryloxycarbonyl, carbamoyl, sulphamoyl, alkyl-, aryl- or heterocyclylaminocarbonyl or -carbonylamino and substituted amino.   
     
     
       2. The process according to claim 1, wherein the aromatic radical A bears a substituent selected from the following group ##STR14## 
     
     
       3. The process according to claim 1, wherein the halonitroaromatic compound of the formula (I) corresponds to the formula Ia, Ib or Ic and the haloaromatic amine of the formula II correspond to the formula IIa, IIb or IIc, ##STR15## where R 1  represents hydrogen or chlorine, n represents 1 or 2 and   R 2  is hydroxy, alkyl, alkoxy, aryloxy, aryl, formyl, alkanoyl, cycloalkanoyl, aroyl, alkanoyloxy, cycloalkanoyloxy, aroyloxy, alkylsulphonyl, cycloalkylsulphonyl, arylsulphonyl, alkanoylamino, cycloalkanoylamino, aroylamino, alkylsulphonamido, cycloalkylsulphonamido, arylsulphonamido, alkoxycarbonyl, cycloalkoxycarbonyl, aryloxycarbonyl, carbamoyl, sulphamoyl, alkyl-, aryl- or heterocyclyl-aminocarbonyl or -carbonylamino and substituted amino.   
     
     
       4. The process according to claim 1, wherein R 2  represents one of the following radicals: ##STR16## 
     
     
       5. The process according to claim 1, wherein the halonitroaromatic compound corresponds to one of the formulae (Id) to (Ig) and the haloaromatic amine corresponds to one of the formulae (IId) to (IIg) ##STR17## where R 1  is hydrogen, ##STR18## 
     
     
       6. The process according to claim 1, wherein the halonitroaromatic compound corresponds to one of the formulae (Id) to (Ig) and the haloaromatic amine corresponds to one of the formulae (IId) to (IIg) ##STR19## where R 1  is chlorine, ##STR20## 
     
     
       7. The process according to claim 1, wherein the catalytic hydrogenation is carried out in an aliphatic water-miscible alcohol having from 1 to 4 carbon atoms. 
     
     
       8. The process according to claim 1, wherein an iron-containing Raney nickel catalyst containing from 1 to 10% of aluminium and from 5 to 30% of iron is used.